Cation exchange due to the diffusion of ammonium from livestock effluent through glacial clay soils

Abstract

The objective of this study was to experimentally simulate interactions between liquid manure and soil in diffusion-dominant areas beneath earthen manure storage (EMS). A previous radial diffusion cell method was modified to include an anaerobic chamber that employed a plastic glove bag supplied with inert Ar gas. Anaerobic conditions were maintained during the entire run time of the experiment. Little oxidation of NH 4 + occurred; consequently, NO 3 - and NO 2 - concentrations were lower than the detection limit. Chloride played a key role in redistribution of major cations and anions resulting from the NH 4 + diffusion. Linear NH 4 + and K + adsorption isotherms were obtained. The resulting distribution coefficients, K d, for NH 4 + ranged from 0.3 to 0.4 L/kg. Significant NH 4 + exchange reactions led to an average increase in hardness of 137% in the reservoirs, due to extraction of exchangeable Ca and Mg. Geochemical mixing modeling using PHREEQC adequately simulated the linear NH 4 + adsorption at low dissolved NH 4 + concentrations (<30 mM). The predicted manure volumes to cause NH 4 + saturation were 1.0–1.4 mL/g for the glacial clay soil samples.